In my R01, I proposed to determine if HIV could integrate in resting CD4+ T cells and to study how activation of T cells affects that process. I showed that, contrary to dogma, integration does occur in resting cells. This work led to an in vitro model of HIV latency and formed the basis for a new paradigm of HIV reservoir formation - that reservoirs may form without T cell activation. As part of these studies, I developed a new, quantitative, highly sensitive assay for HIV integration. This assay is the first that is sensitive enough to measure integration in PBMCs from patients. Prior integration assays lack the necessary sensitivity, thus my assay is a significant advance. Here, I propose to use the new assay to measure integration in subsets of CD4+ cells in vivo (Aim 1). Comparing integration levels in patients off HAART to patients on HAART may provide another way to evaluate the efficacy of therapy. [unreadable] [unreadable] In the process of my R01 research, I also developed an interest and expertise in resting T cell restriction of HIV. Here, I propose to study the restriction of HIV in CD4+ cells, examining both the cellular and viral factors. My integration assay is sensitive enough for use in highly restricted cells. Using the tools that I developed during my R01 studies, I will characterize the restrictions to HIV infection in blood-derived CD4+ cells (Aim 2), and examine the role that auxiliary viral proteins play in overcoming the restriction in resting T cells (Aim 3). Identification of cellular pathways and viral proteins involved in restriction of HIV infection could provide new targets for antiretroviral therapies. [unreadable] [unreadable] My long-term goal is to be an independent physician-scientist who conducts basic research that has clinical relevance. My short-term goal is to obtain this award, because it will guarantee me 75% protected time, which I need in order to focus on my research and make significant contributions to the field. Since becoming an Assistant Professor, I am first or senior author on five publications. I have recently recruited one undergraduate student, two graduate students and a postdoc, with whom I have submitted manuscripts, thus my productivity is increasing. The ability to develop my own niche in HIV research and to obtain funding (6 grants, including an R01) demonstrate my potential for success as an independent physician-scientist. Finally, the letters of recommendation from my department chair, division chief, mentor, and collaborators convey the strong support that I receive at Penn. [unreadable] [unreadable] [unreadable]